†k Original Articles†l Minzoku Eisei

•k Original Articles•l Minzoku Eisei Vol 56: No 4, 168•`177(1990)

Cadmium Content in Rice and Rice Field Soil in China, Indonesia and

Japan, with Special Reference to Soil Type and Daily Intake from Rice

Ida Farida RIVAI*, Hiroshi KOYAMA* and Shosuke SUZUKI*

‡T Introduction

The present study was carried out to: 1)

assess cadmium content in both rice and soil

of China, Indonesia and Japan, 2) determine

the relation of cadmium content in rice and

soil to soil type and country, and 3) estimate the average daily cadmium intake from rice

from the results of cadmium analysis and rice

consumption data of FAO. Much data on cadmium content in rice and

soil of Japan have been reported (Iimura 1981;

Masironi et al., 1977; Morishita 1981; Moritsugu et al., 1964; Nakatsuka et al., 1988;

Yanagisawa 1984), but those for Indonesia are

limited (Suzuki et al., 1988; Rivai et al., 1990).

Moreover, the only data on cadmium content

in rice of China have been reported by Rivai et

al.(1990), none are available on the cadmium

content in soil of China. Rice is a major source

of cadmium intake for man in rice eating

countries such as China, Indonesia and Japan.

Thus, rice may be the best indicator to

monitor cadmium exposure. Iimura (1981) reported the mean cadmium content in brown

rice and paddy soil of Japan to be 90 and 450

ppb, respectively. Yanagisawa et al. (1984) found this parameter in brown rice and paddy

soil from polluted area of Japan to be 0.37 and 1.35 ppm, respectively.

Hutton et al. (1987) found the major sources

of cadmium pollution to the agriculture land in England to be sewage disposal, manufac-

ture and phosphate fertilizer. Morishita

(1981) and Asami (1981) reported that rice

grown in polluted soil contains more cadmium than that of non polluted soil.

However, there are no data on relationship

between cadmium content in rice and soil to

the soil type. Assessment of the accumulation

of cadmium content in rice and soil by soil

type may also facilitate environmental

monitoring.

Daily cadmium intake from rice may be

estimated from cadmium content in rice mul-

tiplied by daily rice consumption. Ohmomo

(1981) reported the daily cadmium intake from rice of Japan to be 26 ,ug/person.

Though the biological role of cadmium is

not known for plants, under certain condi-

tions it may accumulate in some plants to

levels hazardous for animals and finally for

man at the end of the food chain. This

element, after entering into the soil would

not be leached out and thus accumulate.

Some of it is absorbed by plants that are a

part of the ecological cycle. The hydrochloric acid extraction method can be used to detect the soluble fraction of the element absorbable

from the roots of rice plants (Nihon Dojo

Hiryo Gakkai 1986).

‡U Materials and Methods

A total of 178 pairs of rice and soil samples

were collected from China, Indonesia and

*群馬大学医学部公衆衛生学教室

* Department of Public Health, Gunma University School of Medicine

Rivai et al.: Cadmium Content in Rice and Rice Field Soil in China, Indonesia and Japan 169

Japan. Soil samples were also collected from rice fields where rice plants were growing. All

the rice samples were unpollished. Samples

were taken from East, Northeast and South

China. In Indonesia, they were taken from

Java, Sumatra, Kalimantan and Sulawesi,

and in Japan, from Hokkaido/Tohoku,

Hokuriku, Kanto, Tokai, Chugoku, Shikoku

and Kyushu. Sample sites recorded were

usually prefecture or city level.

Pre-treatment of a rice sample: 0.1 gram

of a rice sample was put into a test tube and

weighed, dried in an oven at 105•Ž for 48

hours and weighed again to assess water

content. The dried sample was asked on a hot

plate with 1.0 ml of concentrated nitric acid

(metal free) until dry. Then, 2.0 ml of 14%

nitric acid were added, dissolving the residue

at the bottom of the test tube. Two methods

were used for pre-treatment of a soil

sample: 1) Extraction by HCl without

ashing. About one gram of a dried and filtered

soil sample was put into a test tube and

weighed and then 5.0 ml of 0.1 N HCl was

added. The test tube was shaken in a water-

bath of 30•Ž for 1 hour. The upper clear

solution was separated and centrifuged at

3000 rpm for 5 minutes for cadmium analysis,

2) Extraction by ashing with nitric acid.

About one gram of dried and filtered soil

sample was put into a test tube, weighed, and

5.0 ml of concentrated nitric acid (metal free)

were added, followed by ashing on a hot plate.

10.0 ml of pure water were then added and the

clear supernatant was taken for cadmium

analysis.

Cadmium in the solution was assessed by a

flameless atomic absorption spectrophoto-

meter (Hitachi 180-30), with automatic

background correction. Each sample was

analyzed two or three times by an autosam-

pler at wave length 229 nm for rice samples and 320 nm for soil samples. Under the same

conditions, standard materials provided by

the US National Bureau of Standard were

used for reference to confirm accuracy: 0.1

gram of powdered rice (No. 1568) and 0.5 g of orchard leaves (No. 1571) for soil samples.

The reliabilities of the cadmium determina-

tion in rice, soil extracts by HCl, and in

supernatants of soil ashed by HNO3 were

18.7%, 7.1% and 17.8%, respectively, in terms

of the coefficient of variation of 10 repeated

analyses of the same sample lot. A recovery

test was made by adding 0.002ug of cadmium

to each five sample of rice (0.1 g) from the

same sample. The recovery rate was 94% on

the average, ranging from 74% to 118%.

Identification of soil type was based on the "Soil Map of the World"

, Volume VIII (1978) and Volume IX (1979) by FAO (Food and

Agriculture Organization). A few samples on

a borderline between two soil types were

excluded.

Daily cadmium intake from rice was cal-

culated by cadmium content in rice multiplied by daily rice consumption from Food Balance

Sheets, 1979-1981 Average, by FAO (1984).

‡V Results

Geometric mean and geometric standard

deviation of cadmium content in the 178 pairs

of rice and soil samples from China, Indonesia

and Japan are shown in Table 1. Geometric

mean concentration of cadmium in rice was

11.8, 20.3 and 75.9 ng/g for China, Indonesia

and Japan, respectively, and that in soil from

China, Indonesia and Japan, 33.1, 20.1 and

81.4 ng/g, respectively, by the hydrochloric

acid extraction method, and 99.5, 73.7 and

170 Minzoku Eisei Vol 56: No 4,1990, 1990,7

Table 1 Geometric means and deviations of cadmium content (ng/g wet wt.) of 178 pairs of rice and soil samples from the three countries.

Note : Cd, cadmium ; N, number of samples ; GM, geometric mean ; GD, geometric

deviation ; (a), extracted by hydrochloric acid ; (b), ashed by nitric acid ;

ANOVA, F=26.3, 36.6 and 120.5 at p<0.01, for Cd in rice, (a) and (b), respec-

tively.

Table 2 Geometric means and deviations of cadmium content of 178 pairs of rice (ng/g wet wt.) and soil (ng/g dry wt.) samples grouped according to

soli type.

Abbreviations and marks : See the footnote of Table 1; *, the mixed soil of Andosols,

Lithosols, Histosols and Acrisols ; ANOVA, F=6.2, 8.6 and 25.7 at p<0.01, for Cd in

rice, (a) and (b), respectively.

445.8 ng/g, respectively, by the nitric acid

ashing method. Cadmium content in the rice

and soil of Japan was two to several times

higher than in the other two countries. The

cadmium content in rice of China was lower

than that of Indonesia, though in soil ashed

by the nitric acid in China higher than that of

Indonesia.

Table 2 shows the difference in cadmium

content in the 178 pairs of rice and soil

samples broken down by soil type. Seven soil

types were identified from the 178 collection

sites as: Andosols, Cambisols, Fluvisols,

Gleysols, Histosols, Luvisols and Acrisols.,

"Mixed soil" was given to sample sites having

more than one soil type. Cadmium content in

rice grown on the soil type of Fluvisols, all

from Japan, was highest or 164.0 ng/g, and

that of Gleysols lowest or 12.2 ng/g. Twelve

samples out of 15 Gleysols, were from China

(Tables 2 and 3). Cadmium content in soil by extraction with hydrochloric acid and by

ashing with nitric acid showed the data of

Cambisols, all samples from Japan, to be the

highest or 148.4 and 601.8 ng/g, and that of

Histosols, lowest or 12.2 and 36.6 ng/g, respec-

tively. Differences in cadmium content in the 178 pairs of rice and soil samples by soil type


Figure 1 Relationship between cadmium content in rice and soil

extracted by hydrochloric acid.

Table 3 Numbers of rice samples collected from China, Indonesia and Japan broken down into seven soil types.

*

, see foot note of Table 2,

were statisticaly significant at p<0.01.

The number of soil types collected from

China, Indonesia and Japan is shown in Table

3 broken down by soil type. Soil types in a

country were grouped into only one or two.

Gleysols and Mixed soils were the only soil

types found in China. Soil types in Indonesia

were comprised of Andosols, Histosols, Luv-

isols and acrisols. In Japan, the soil type was

mainly of Andosols (73%) the rest being

Cambisols, Fluvisols, Gleysols and mixed soil.

The mean ratio of cadmium concentration

in rice to that in soil (a) was 0.89 of 178 paired

samples, as shown in Table 4. This ratio differed by soil type ranging from 0.26 for

Gleysols to 2.32 for Fluvisols. Thus, Fluvisols

of Japan showed the highest biological con-

centration from soil (b) to rice, though the

ratio of cadmium concentration in soil (b) to

in soil (c) is low.

Figure 1 shows the relationship between

the concentration of cadmium in rice and that

in soil extracted by hidrochloric acid (a) clas-

172 Minzoku Eisei Vol 56: No 4, 1990, 7

Table 4 Geometric mean ratios of cadmium content in rice to soil extracted by hydrochloric acid (a) and soil ashed by nitric acid (b) broken down by soil type.

Abbreviations and marks : GM, geometric mean ; GD, geometric deviation ; *, see

foot note of Table 2 ; ANOVA, F=3.65, 3.36 and 4.82 at p<0.01, for rice/a, rice/

b and a/b, respectively.

Table 5 Geometric means and deviations of cadmium content in rice

grown on the soil type of Andosols and Gleysols by country (ng/g wet wt.).

Abbreviations : N, number of sample ; GM, geometric mean ; GD, geometric

deviation ; p, level of statistical significance.

sif ied by soil type and indicates rice grown in

the soil of Fluvisols of Japan to contain the

most cadmium, though the cadmium content

in the soil was not high. Gleysols in China

contained less cadmium in rice but inter-

mediate amounts were present in the soil.

The geometric mean and geometric stand-

ard deviation of cadmium content of rice

grown on a same soil type but in different country are shown in Table 5. Cadmium

content in rice grown on Andosols in Japan

was 70.1 ng/g which is higher than that of

Indonesia or 17.6 ng/g. Rice grown in Gleysols

in Japan was 81.4 ng/g, and had more cad-

mium than that in China, 7.4 ng/g.

The coefficient of correlation between the

concentrations of rice and soil is shown in

Table 6 in each country. In china and Japan,

negative correlation was seen between cad-mium in rice and in soil extracted by the

hydrochloric acid, but a positive significant

value was found for Indonesia (r=0.32,

p<0.05). Relationships of cadmium content in rice to that in the soil ashed by nitric acid

from China, Indonesia and Japan were not

significant. The correlation coefficients be-

tween cadmium content in soil (a) to that in soil (b) were 0.53 and 0.68, these being signifi-

cant at p<0.01 for Indonesia and Japan, re-

spectively. The correlation coefficient be-


Table 6 Correlation coefficients between concentration of cadmium in

rice and soil samples by country.

Abbreviations and marks : Cd, cadmium ; (a), extracted by hydrochloric acid ;

(b), ashed by nitric acid ; * & * *, significant correlation at p<0.05 & p < 0.01,

respectively.

Table 7 Estimation of daily cadmium intake from rice by country

(microgram/person)',

*, Average daily rice consumption (g/person) of 1979-1981 from the data of

Food Balance Sheets by FAO (1984).

tween cadmium content in rice and soil ex-

tracted by hydrochloric acid (r=0.25) and soil

ashed by nitric acid (r=0.39) was positively

significant at p<0.01. A positive significant

correlation was obtained also for the relation-

ship of cadmium content in soil extracted by hydrochloric acid (a) to soil ashed by nitric

acid (b) (r=0.71, p<0.01). Among the three countries investigated,

the daily cadmium intake from rice of Japan

was highest or 22.8 ,ug with a 95% confidence

limit from 3.8 to 136.8 ,ug. Mean daily cad-

mium intakes from rice in China and in

Indonesia were estimated to be 4.1 and 13.3

,ug, respectively (Table 7).

‡W Discussion

Cadmium content in the rice of Japan as

reported by several researchers were: 65 ng/g

wet wt. (Masironi et al.,1977), 52 ng/g dry wt.

(Nakatsuka et al., 1988), 66 ng/g dry wt.

(Moritsugu et al., 1964), 90 ng/g dry wt.

174 Minzoku Eisei Vol 56: No 4,1990, 1990,7

(Yamagata et al., 1978) and 137 ng/g wet wt.

(Yanagisawa et al., 1984). The Cadmium con-tent in the unpolished rice of Indonesia or 26.3 ng/g wet wt. was somewhat less than the

previous data of cadmium content in unpol-ished rice of Java in Indonesia by Suzuki et al.

(1980) or 39 ng/g dry wt. when corrected to 13% of water content in the samples. Unfor-

tunately, data on cadmium content in rice and

soil of China were not available.

Cadmium content in rice of China was

significantly lower than that of Indonesia,

though the soil in China contains more cad-

mium than that in Indonesia. Probably, some

different conditions between China and

Indonesia influence cadmium absorption

from soil by rice plants such as the pH of soil,

water (irigation), method of agriculture and

variety of rice. Thornton et al. (1980) found

the availablity and uptake of cadmium by

plants to decrease with increasing soil pH of 6.5 or more. Cadmium content in soil also

varies depending on the depth of the soil as

reported by Hamilton (1980). Samples taken

close to the surface or the soil depth of 0-7.5

cm contains more cadmium than those locat-

ed deeper.

The soil type Fluvisols found only in Japan

contained the highest level of cadmium in

rice. Possibly, cadmium in this soil type may

be absorbed most easily by rice plants com-

pared to other soil types. Fluvisols had devel-oped from recent alluvial deposits and uncon-

solidated materials (FAO 1978; 1979). Matsuzaka (1982) reported Fluvisols in Japan

mainly appear along sea coasts. Hokuriku

of Japan has been known as a high cadmium

area and is located along the Japan Sea.

Fluvisols is equivalents to Entisols according

to the U.S. Soil Classification of 1949 System

(Brady 1984), which is the component of mineral soil materials. Large amounts of

cadmium in soil (up to 30 ppm) may be

present in mineralized areas of England

(Thornton et al., 1980). Half of the soil samples in China was

comprised of Gleysols which contains the

lowest cadmium in rice. Gleysols develops in

plains and deltas where better natural or artificial drainage have resulted in the ripen-

ing of materials containing little sulfide or

neutralizing components that prevent strong

acidification following oxidation of the sul-

fides upon drainage (FAO 1978; 1979). Cad-

mium content in rice grown in 81 out of 85

soil types of Andosols of Japan was higher

than in the same soil type of Indonesia. One

sixth of the total area of Japan is reported to

be covered by the soil type Andosols

(Matsuzaka 1982). Gleysols of Japan also con-tains higher cadmium in rice than in China.

Cambisols contained the highest cadmium

in soil (a) and (b), and Histosols was lowest.

Cadmium may thus possibly accumulate more easily in Cambisols. Cadmium content

in the soil of Houston, Texas (Suzuki et al.

1982) which occurs in three different colors

showed the geometric mean of cadmium con-

tent in black soil (37.7 ng/g) to be significan-

tly higher than that of white soils (17.6 ng/g)

and grey soils (21.5 ng/g) when extracted by

nitric acid. No differences in cadmium con-

tent in black, white and gray solis could be

found when extracted by acetic acid. There-

fore, the color of the soil may give some

information on cadmium content in soil.

Cadmium content in soil ashed by nitric

acid (b) was three to five times higher in the

three countries compared with that in soil

extracted by hydrochloric acid (a). This is in


agreement with the data of Suzuki et al.

(1982) that nitric acid extracts more cadmium from rice than acetic acid does. Although the

extraction by the hydrochloric acid method is

reported suitable to detect the soluble or

mobilizable fraction of the element (Nihon

Dojo Hiryo Gakkai 1986), the data of this

study show that the relationship between

cadmium content in rice and in soil ashed by

nitric acid (b) have a higher correlation coeffi-

cient than in the case of soil extracted by

hydrochloric acid (a).

Daily cadmium intake from the rice of

Japan or 22.8 microgram/person is highest among the three countries. However, the

daily cadmium intake from rice of Japan is

somewhat less compared to the data of

Ohmomo (1981) or 26 microgram/person.

Cadmium content in the rice of Indonesia was

three times less than that of Japan but the

daily cadmium intake from rice in Indonesia

was less than half that of Japan. Daily cad-

mium intake from rice not only depended on

cadmium content in rice but also on the daily

rice consumption of each country. FAO

(1984) reported daily rice consumption of

Japan (300.2 g/person) to be lower than that of Indonesia (507.3 g/person).

This study indicates geographical deffer-

ence to have greater influence on cadmium

content in rice and soil. The difference may

largely come from natural origin, and in some

localized places man made pollution play a

major role.

‡X Summary

Cadmium content was assessed for 178

pairs of rice and soil samples collected from China, Indonesia and Japan from 1986 to

1988. The samples were also divided into

eight groups by soil type. Geometric mean

content of cadmium in rice was 11.8, 26.3

and 75.9 ng/g for China, Indonesia and Japan,

respectively. Geometric mean cadmium con-

tent in soil from China, Indonesia and Japan

was 33.1, 20.1 and 81.4 ng/g, respectively, by

the hydrochloric acid extraction method, and

99.5, 73.7 and 445.8 ng/g, respectively, by the

nitric acid ashing method. Cadmium content

in soil ashed by nitric acid was several times

higher than that extracted by hydrochloric

acid of the same sample. The soil type of

Fluvisols was found only in Japan, and 12 out

of 15 Gleysols samples were found in China.

The highest cadmium level in rice was found

in Fluvisols samples and the lowest was in

Gleysols. Cambisols contained the highest

cadmium level in soil, and Histosols the low-

est. Cadmium content in rice and soil and

daily cadmium intake from rice were highest

in Japan among the three countries. The

relationship of cadmium content in rice to soil

was low within a country. The geographical

or country factor determined, to a greater

extent, cadmium content in rice and soil than

soil type.

‡Y Acknowledgments

This survey was supported by Grant-in-Aid

of Ministry of Education, Science and Cul-

ture, Japan (#58030010, #58041014 and

#0150283). The authors thank the agricul-

tural experiment stations of Gunma Prefec-

ture of Japan, Dr. Qi Gua Xing of China and

Mr. Rafki Abdullah of Indonesia for kindly

providing the rice and soil samples. Thanks are also due to Dr. Masayuki Ogawa and Miss

Chiyono Moriyama for their kind assistance.

176 Minzoku Eisei Vol 56: No 4, 1990, 7

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〔原著〕

中国,インドネシアおよび日本のコメおよび水田土壤中の

カドミウム濃度,特に土壤型および一日摂取量との関連

イダ・ファリダ・リファイ小山洋　鈴木庄亮

　1986～88年に,中国,インドネシアおよび日本

から178対のコメおよび水田土壤が収集され,その

中のカドミウムが定量された.これらのサンプル・

はまた土壤型によって8群に分けられた1コメの

中のカドミウム濃度の幾何平均値は,中国,イ

ンドネシアおよび日本でそれぞれ,33.1,26.3およ

び75.9ng/gであった.水田土壤の中のそれは,同

じくそれぞれ,塩酸抽出の場合33.1,20.1および

81.4ng/g,硝酸灰化の場合99.5,73.7および445.8

ng/9であった.このように,水田土壤の中のカド

ミウム濃度は硝酸灰化の場合のほうが塩酸抽出よ

りも数倍高かった.土壤型Fluvisolsは,日本にの

み見出され,Gleysolsは15中12試料が中国に見出

された.コメのカドミウム濃度は,Fluvisolsで最

も高く,Gleysolsで最も低かった.水田土壤のそ

れは,Cambisolで最も高く,Gleysolsで最も低

かった.コメおよび水田土壤中のカドミウム濃度

およびコメからの1日摂取量は幾何平均値で,こ

れら3力国の中では日本が最も高かった.コメと

水田土壤のカドミウム濃度間の関係は各国内では

相関が低かったが,地域(国)間では相関が高い.

コメと水田土壤のカドミウム濃度は,土壤型より

も地域(国)によって大きく規定されていること

が認められた.

(受稿1989.12.21)

Documents

†k Original Articles†l Minzoku Eisei